1. Field of the Invention
The present invention relates generally to an injection molding apparatus and, in particular, to a valve pin mechanism for use in an edge-gated injection molding apparatus.
2. Related Art
Edge gating from a nozzle of an injection molding apparatus through a number of edge gate tips is well known. A multi-cavity edge, or side, gated injection molding apparatus is described in U.S. Pat. No. 5,494,433 to Gellert, issued Feb. 27, 1996, which is incorporated by reference herein in its entirety. Generally, the multi-cavity edge-gated injection molding apparatus includes several nozzles that are coupled to a manifold to receive a melt stream of moldable material therefrom. Each nozzle is mounted in a cylindrical opening in a mold to convey pressurized melt through a nozzle melt channel to mold gates, which lead to mold cavities in the mold. The mold cavities are spaced radially around the nozzle. Each mold gate extends through a gate insert, which is held in position by a gate insert retainer plate. Each mold gate is aligned with a gate seal that is threadably coupled to the nozzle. As such, the location of the gate seals is generally fixed relative to the mold.
A multi-cavity edge gated injection molding apparatus with a first nozzle, a nozzle link, and a second nozzle is described in U.S. Published Application Publication No. 2005-0196486 A1, published Sep. 8, 2005, which is incorporated by reference herein in its entirety. U.S. Published Application Publication No. 2005-0196486 does not disclose a valve pin mechanism for opening and closing communication to the mold gates.
An edge gated injection molding nozzle including a valve pin mechanism is disclosed in U.S. Published Patent Application Publication No. 2006-0233911 A1 to Spuller, published Oct. 19, 2006. However, the nozzle of the Spuller publication includes a nozzle melt channel on either side of the valve pin. In such an arrangement, melt distributed to the cavities on either side of the valve pin travel different distances, and may therefore lead to a melt flow imbalance towards the lateral gates.